Searchable custom field


I want to create custom field with link to User. i want this field to show only users with role projects manager. right now it shows all the users in that field. how can i do it ?


im getting following message,while creating new permission rule with level 1 having level 0 already created.

“For Projects Manager at level 1 in Project in row 1: Create, Submit, Cancel and Amend only valid at level 0”

You cannot check those in higher level permissions.